Once in a 'blue moon' on Tuesday...but there's a catch

On Thursday Aug. 20, a relatively rare event will take place in the skies above you—it's called a blue moon.

Why it occurs is somewhat complicated. A full moon, when no shadow from Earth covers the lunar body, happens every 29.5 days. Normally this means that there will be 12 full moons a year and three per season. However, once every 2.7 years there will be an extra full moon in one of the four seasons. When this occurs, the third of the four full moons is called a "blue moon." This was devised by Native Americans who gave names to each full moon and then passed it on to the first European settlers.

People have been confused as to what a blue moon really is after an expert mistakenly told "Sky & Telescope" magazine in 1943 that the 1937 Maine Farmers Almanac revealed that a blue moon occurs when any particular month had two full moons. A widely read 1946 article in Sky & Telescope confimed this.

However, the magazine did not rest on its laurels. Editors examined more than 40 editions of the Maine Farmers Almanac from 1819 to 1962 and found references to several blue moons—and all were based on an extra full moon per season—not the two full moons in a month version.

BUT WAIT. Before you plan to watch the full moon, you'll probably be very disappointed. (continue)

Published: August 20, 2013 -- 20:18 GMT (13:18 PDT)

Caption by: Andy Smith

The colors you'll see from the moon might be orange, red, and its normal yellow. The infrequency of blue moons originated the expression, "once in a blue moon."

Published: August 20, 2013 -- 20:18 GMT (13:18 PDT)

Caption by: Andy Smith

Here's a photo of the 2004 blue moon, probably made with a blue filter. This year Photoshop programs will probably be going crazy.

Published: August 20, 2013 -- 20:18 GMT (13:18 PDT)

Photo by: NASA

Caption by: Andy Smith

Be careful. This is what happens from too much exposure to the blue moon.

(The Blue Man Group)

Published: August 20, 2013 -- 20:18 GMT (13:18 PDT)

Photo by: Wikipedia

Caption by: Andy Smith

One moon that is really shows some blue is one of the Saturn moon of Titan. Scientists believe a band of hazy blue layers near the south pole of the only moon in our solar system that contains an atmosphere.

Published: August 20, 2013 -- 20:18 GMT (13:18 PDT)

Caption by: Andy Smith

Another Saturn moon, called Mimas or the Death Star moon shows a bluish band near the equator of the icy moon.

On Tuesday night you can see a relatively rare event - a blue moon. But there's a good chance you'll be disappointed.

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On Thursday Aug. 20, a relatively rare event will take place in the skies above you—it's called a blue moon.

Why it occurs is somewhat complicated. A full moon, when no shadow from Earth covers the lunar body, happens every 29.5 days. Normally this means that there will be 12 full moons a year and three per season. However, once every 2.7 years there will be an extra full moon in one of the four seasons. When this occurs, the third of the four full moons is called a "blue moon." This was devised by Native Americans who gave names to each full moon and then passed it on to the first European settlers.

People have been confused as to what a blue moon really is after an expert mistakenly told "Sky & Telescope" magazine in 1943 that the 1937 Maine Farmers Almanac revealed that a blue moon occurs when any particular month had two full moons. A widely read 1946 article in Sky & Telescope confimed this.

However, the magazine did not rest on its laurels. Editors examined more than 40 editions of the Maine Farmers Almanac from 1819 to 1962 and found references to several blue moons—and all were based on an extra full moon per season—not the two full moons in a month version.

BUT WAIT. Before you plan to watch the full moon, you'll probably be very disappointed. (continue)